Short answer - it isn't likely to change much. In order to significantly affect the overall bitcoin issuing rate long-term, the hash rate would have to continu

Short answer - it isn't likely to change much. In order to significantly affect the overall bitcoin issuing rate long-term, the hash rate would have to continue to grow exponentially for an extended amount of time - years. In reality, the hash rate can only grow exponentially while an older mining technology is being supplanted by a newer one. It happened already with CPU to GPU/FPGA, and now it's happening again with GPU/FPGA to ASIC. It will grow exponentially while everyone hashing upgrades to ASICs, but once the hashing market is saturated with them, it will drop back to modest linear growth, as the only growth will be either new miners coming online or modest, linear improvements in ASIC technology. Haven't looked at this part, but I have a feeling that the difficulty itself wouldn't be able to go high enough to support long-term exponential growth in hashrate.